Instrument for electrosurgical tissue treatment

Abstract

Systems and methods are provided for applying a high frequency voltage in the presence of an electrically conductive fluid to create a relatively low-temperature plasma for ablation of tissue adjacent to, or in contact with, the plasma. In one embodiment, an electrosurgical probe or catheter is positioned adjacent the target site so that one or more active electrode(s) are brought into contact with, or close proximity to, a target tissue in the presence of electrically conductive fluid. High frequency voltage is then applied between the active electrode(s) and one or more return electrode(s) to non-thermally generate a plasma adjacent to the active electrode(s), and to volumetrically remove or ablate at least a portion of the target tissue. The high frequency voltage generates electric fields around the active electrode(s) with sufficient energy to ionize the conductive fluid adjacent to the active electrode(s). Within the ionized gas or plasma, free electrons are accelerated, and electron-atoms collisions liberate more electrons, and the process cascades until the plasma contains sufficient energy to break apart the tissue molecules, causing molecular dissociation and ablation of the target tissue.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]The present application is a continuation-in-part of PCT filed Jun. 27, 2003, and U.S. patent application Ser. No. 10 / 187,733, currently pending, filed Jun. 27, 2002, which is a continuation-in-part of U.S. patent application Ser. No. 09 / 457,201, currently pending, filed Dec. 6, 1999, which is a continuation-in-part of U.S. patent application Ser. No. 09 / 248,763, filed Feb. 12, 1999, now U.S. Pat. No. 6,149,620, which claims benefit from U.S. Provisional Application Nos. 60 / 096,150, filed Aug. 11, 1998 and 60 / 098,122, filed Aug. 27, 1998, the complete disclosures of which are incorporated herein by reference for all purposes.[0002]The present invention is also related to commonly assigned co-pending U.S. patent application Ser. No. 09 / 177,861, filed Oct. 23, 1998, and application Ser. No. 08 / 977,845, filed Nov. 25, 1997, which is a continuation-in-part of application Ser. No. 08 / 562,332, filed Nov. 22, 1995, and U.S. patent application S...

AI Technical Summary

Benefits of technology

[0024]In a specific configuration the electrosurgical instrument comprises platinum or platinum-iridium electrodes. The platinum/platinum-iridium electrodes have a low resistivity and low thermal conductivity which minimizes the production of heat in the electrodes and the electrically conductive fluid and allows more electrical energy to be applied directly into the conductive fluid. As the electrically conductive fluid flows between the active electrode(s) and the return electrode(s), the high frequency voltage is sufficient to non-thermally vaporize the electrically conductive fluid (e.g., gel or saline) between the active electrode(s) and the tissue. Within the vaporized fluid, an ionized plasma is formed and charged particles (e.g., electrons) are accelerated towards the tissue to cause the molecular breakdown or disintegration of several cell layers of the tissue.

[0025]In another variation of the invention, the inventive device may include a tissue treatment surface configuration th

Problems solved by technology

These traditional electrosurgical techniques for treatment have typically relied on thermal methods to rapidly heat and vaporize liquid within tissue and to cause cellular destruction.

This current, however, may inadvertently flow along localized pathways in the body having less impedance than the defined electrical path.

This situation will substantially increase the current flowing through these paths, possibly causing damage to or destroying tissue along and surrounding this pathway.

One drawback with this configuration, however, is that the return electrode may cause tissue desiccation or destruction at its contact point with the patient's tissue.

Another limitation of conventional bipolar and monopolar electrosurgery devices is that they are not suitable for the precise removal (i.e., ablation) or tissue.

At the point of contact of the electric arcs with tissue, rapid tissue heating occurs due to high current density between the electrode and tissue.

The tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site.

The use of electrosurgical procedures (both monopolar and bipolar) in electrically conductive environments can be further problematic.

However, the presence of saline, which is a highly conductive electrolyte, can cause shorting of the active electrode(s) in conventional monopolar and bipolar electrosurgery.

Such shorting causes unnecessary heating in the treatment env

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